Fetal Alcohol Spectrum Disorders (FASD) are a range of permanent birth defects caused by maternal alcohol consumption during pregnancy. The prevalence of FASD in populations of younger school children is recently estimated as high as 2-5% in the United State and is more common than Down syndrome and autism. FASD-related costs are more than $6 billion annually. Identification of the mechanism of ethanol toxicity in the brain and determination of the effective therapeutic target(s) are cited as importat goals in the NIAAA Strategic Plan for 2009-2014. Central nervous system (CNS) damage is a major feature observed in FASD patients. The cerebellum is one of the most sensitive areas in the CNS to ethanol toxicity. Neuronal loss is one of the most deleterious effects of ethanol and is responsible for many of the behavioral deficits observed in FASD. In the animal model, exposure of infant rodents to ethanol during a portion of the brain growth spurt period - postnatal day (PD) 4 to 9, equivalent to the human third trimester - causes a significant loss of cerebellum Purkinje and granule neurons. However, the underlying mechanism for ethanol-induced neuronal loss in the developing cerebellum is still largely unclear. The goal of this proposed study is to identify the mechanism underlying ethanol neurotoxicity and the novel target(s) for the prevention and treatment of FASD. The double-stranded RNA (dsRNA)-activated protein kinase (PKR) organizes the cellular self-defense system in response to diverse physiochemical stresses or viral infection by regulating a variety of downstream target proteins and signal pathways. Activation of PKR by its intracellular activator RAX under physiochemical stress conditions leads to protein synthesis inhibition as well as apoptosis and has been implicated in the pathogenesis of a number of neurodegenerative diseases. The central hypothesis of the proposed study is that RAX-mediated PKR activation regulates ethanol- induced neuronal loss in the developing cerebellum. Specific Aim 1: To investigate whether PKR activation through RAX/PKR interaction regulates ethanol- induced neuronal apoptosis in the developing cerebellum of the mouse. Specific Aim 2: To determine whether inhibition of PKR by targeting RAX or PKR expression or by PKR inhibitors alleviates ethanol-induced neuronal loss in the developing cerebellum of the mouse. Specific Aim 3: To determine whether RAX+/- mice, N-PKR-/- mice or PKR-inhibitor-injected mice are more resistant to ethanol-induced cerebellar behavioral dysfunction.